The present invention relates to paperboard containers for potable liquid and more particularly to rectangular cross-sectional containers formed from a one-piece substantially T-shaped blank of polyethylene coated paperboard. Such containers are generally of the type shown in U.S. Pat. No. 3,749,330, granted July 31, 1973, to Charles W. Jones, U.S. Pat. No. 4,084,489, granted Apr. 18, 1978, to Matovich, Jr., and U.S. patent application Ser. No. 911,900, filed June 2, 1978, by Josef Buschor. The distinguishing characteristics of these cartons are their inclusion of a straw element within the interior of the carton blank which, during opening of the carton, may be rotated to expose one end of the straw element from which the contents of the carton may be drawn, and the deposition of the top and bottom end panels of the carton substantially perpendicular to the sidewalls. Such characteristics provide convenience and sanitary usage of the contents of the container while permitting more efficient use of paperboard material and yielding improved carton stacking for shipment.
Although these containers have provided a significant improvement over prior art gable top container designs, they have possessed certain structural and fabrication deficiencies which have prevented their widespread use in the industry. These deficiencies have focused upon material loss or waste in the nesting of multiple carton blanks upon the sheet stock from which they are derived, a tendency for leakage at the top corner seals of the carton, and damage to the carton blank paperboard during the scoring and bending of the carton blank.
With reference to the material wastage during fabrication of the carton blanks, the prior art, such as Matovich, Jr., U.S. Pat. No. 4,084,489, has disclosed a carton blank in which the width across the side panels and end sealing tabs has been substantially greater than the combined width of the end closure panels. This dimensional relationship has required the carton blanks to be nested upon the sheet stock from which they are produced, in a manner whereby the carton blanks are separated from one another. By such separation, voids are formed between adjacent carton blanks upon the sheet stock, which results in substantial sheet stock waste and decreases machine cutting speed operation.
The corner leakage tendency of the prior art cartons has been caused primarily due to the inclusion of V-shaped notches upon the sealing tabs of the blank which has resulted in the raw cut edges of the sealing tab being located at the corner junctions of the side panels with the end closure panels of the container. These raw cut corners are subject to being wetted by the contents of the carton and yield small discontinuities in the sealing surfaces which has been found to prohibit the effective sealing of the end closure panels thereto. Thus, the prior art carton has been subject to moderate leakage at the top corner junctions between the end panels and side panels.
Additionally, the prior art carton blank design has heretofore prohibited the side sealing tab from being sealed onto both the top and bottom end closing panels of the carton. As such, during the subsequent end sealing operation of the end closure panels to the side panels, a small inconsistency or flow channel has been present in the corners of the carton adjacent the end panel/side sealing tab junction which often allowed small amounts of the contents of the carton to be released during shipping and handling.
To facilitate formation of the carton, the prior art carton blank has been pre-scored to provide preferred bending lines about which the carton is articulated. Heretofore, the bending of the carton blank was accomplished in a direction away from the scoring line, i.e., such that the carton blank breaks away from the score lines. This bending produced a bulging effect at the corners of the container and resulted in the rupturing of the paperboard fiber during the bending process which detracted from the overall appearance of the container, as well as oftentimes fracturing the polyethylene coating of the carton blank making the container subject to absorbtion of the contents therein.
Thus, there exists a present need in the art for a carton blank wherein material wastage is maintained at a minimum, the corner areas of the carton are eliminated from raw cut edges, and the scoring and bending of the carton blank is adapted to eliminate rupturing of the fibers of the paper stock material.